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For Voyager (from Incitatus)

Discussion in 'The Pub' at netrider.net.au started by incitatus, Nov 16, 2006.

  1. Hi there, remember our coffee night conversation about military shotguns and their effects? I dug out an old manual and came up with these figures. Now I'm no physicist, but I don't see a problem with the effect discussed.

    A typical energy figure for the common high-brass ("maximum") 12 gauge solid (un-rifled) round is 2360 ft. lbs. I don't have figures for a rifled round, but it can only be higher.


     
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  2. If its only for 1 person, isn't that a... PM :?
     
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  3. Possibly.....but I'm bored :grin:
     
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  4. Re: Just for Voyager (from Incitatus)

    If you were, youd provide us a metric conversion!

    Not knowing the conversation but it would depend on the rifled round;

    ie, .22 vs 30-06 vs .444
     
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  5. Re: Just for Voyager (from Incitatus)

    No, I'm talking about a rifled 12 gauge solid round, like these

    [​IMG]
     
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  6. Aaaah, now it makes sense...

    So why would a solid coming from a rifled barrel have a higher energy?

    I would have thought the rifling will only help its path/accuracy not its muzzle exit energy.

    Do all solids use a sabot? If not, would'nt the sabot slow it down, even in a rifled barrel?
     
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  7. We are not talking about a rifled barrel, it's a shotgun. We are talking about a rifled round, and the reason the velocity at the muzzle is higher is aerodynamic, i.e. rotation means less induced drag and greater acceleration. No, not all solids use a sabot, mainly rifled solids. Unrifled solids can be as simple as a spherical 'lethal Ball'...
     
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  8. i've seen what they do to wild boars...... lets just say the area that got shot doesn't need to be minced at the butchers!!

    the rifled rounds can have a more drag inside the barrel but as you have pointed out, once fired the induced rotation incurres less accrued drag in flight (if that all made sense) as well as the ratation holding true to the trajectory more than a not rotating projectile.

    its also the reason a lot of bowhunters use helical fletches and target archers dont (there are different systems for target archers to use)

    the rotating arrow is slower but holds accuracy better which is used to offset the extra drag and wind divertion cause by the hunting tip. target archers prefer the higher speed thus giving accuracy by having the arrow in the air (and subject to its effect)for the shortest time possible. Variation on both these ideas are also widely used.

    um yeah now back to shotguns...... BANG!
     
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  9. Are you sure??

    Heres something from our German friends from Brenneke:

    "The first sabot worthy of the BRENNEKE® name

    The new »SuperSabot« was literally designed from the ground up for 12 gauge rifled shotguns, completely redefining sabot technology (firing subcaliber projectiles from a rifled shotgun barrel)."

    Taken from:
    http://www.brenneke.de/brenneke_engl/web/text/2_1_3super_text.html

    Your theory of velocity is fine... however, if the sabot round is compared to a round without and Kinetic Energy= 1/2mv^2, reducing the Mass in the equation when the sabot drops may keep the velocity higher and more accurate, but not necessarily as powerful - assuming you the velocities are equal at exit (this might be the flaw in my counter theory) - Additionally, I would think a rotating projectile does not have less resistance/drag, only better penetration - remembering there are two types of drag in play - 1. Surface - aka boundary layer drag (minimal) 2. Turbulent Drag - (Major caused by the projectiles shape - Major) - in this case identical, becuase all we are really talkin about is two projectiles, one rotating and one not. Of course all this is based on the rounds not being rifled, but the barrel.


    Cheers,

    Moto
     
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  10. a bog standard shotgun is NOT rifled as it has no real need to be.

    so they put the rifling on the projectile to achive the desired result
     
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  11. Yes totally, in this case we are talking about military shotguns used for house clearing and tunnel work, where accuracy and range are completely irrelevant, stopping power being the only issue. In fact in tunnel work, the barrel lengths are sometimes cut down by as much as 30%.
     
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  12. I know and understand this, just needed to clarify, because there is such a thing as a rifled shotgun barrel as quoted above.

    Cheers,

    Moto
     
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  13. yeah i know... sparts shotty's maybe but as Inci has said... derfinately not combat shotguns. And hardly worth it for blasting bunnies and foxes
     
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  14. Ok, now it all makes more sense.

    So if we took a two identical 12 Gauges and a rifled Sabot and a not Rifled Sabot, you believe the rifled sabot has more punch?
    This is what Im unsure about, because I believe, both leave the barrel at the same velocity, both have the same amount of turbular drag so both will drop at the same rate. Only difference is the round which had the rifled sabot will travel straighter (excluding drop as it is identical due to the cause of gravity) because its rotating.
    Finally, the rifling may even slow it down, becuase rifling is designed to be an interference fit in the barrel to induce rotation - but hey, i have no idea what tolerancing the rounds or the barrels are made to.

    Does the above make any sense? Im open to correction here.

    Moto
     
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  15. Yes it does all make sense, and we are not talking about large differences here. There is just one factor you have missed though. Rotation starts in the barrel, and the effects of drag are actually greatest in the barrel because of the compression wave built up in front of the round and constrained by the barrel dimensions (Boyles law, PxV=C comes into play). Rotation also creates an 'air bearing' that reduced friction. The net result of both less drag and less friction is greater acceleration while in the barrel, and as I am sure you know, acceleration becomes deceleration immediately the round leaves the barrel.
     
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  16. Motard, You not quite there refer Drews post below.

     
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  17. I stand corrected. Yep missed that one.
    Damn you Boyle. :grin:
     
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  18. Sorry, I only agree with half of this explanation. Yes its more accurate due to gyroscopic stability... No it does not have less drag, just because its rotating - as briefly explained earlier. Especially when supersonic... Ill need some time if you want me to explain why with relation to sonics (Theres a very big difference in drag coefficients between Mach 0.9 and 1.1).

    However, Inci's introduction of Boyles Law into the argument has defined and settled the discussion.
     
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  19. Re: Just for Voyager (from Incitatus)

    that would make a nasty hole in almost anything... imagine poor dumbo when you let go with one of those sadistic bastards...
     
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  20. I've still got a couple of packets of solids for mums old 410, they make a nice hole in a bunny at close rangewhen you can hit the damn things.

    from memory there a rifled round.
     
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